The correct intracellular targeting of protein kinases and phosphatases confers specificity to the enzymes, in placing them in close proximity to their preferred substrates. Targeting of these enzymes occurs via associati specific proteins which are found in different locations in the cell. The central theme of our research progr^ understand the structural basis for the regulation of the activity and spatiotemporal organization and of th and lipid second messenger signaling cascades. In particular, changes in interactions between specific partners can alter the lifecycle and/or subcellular localization of the respective protein kinases (PKs). In this application, we propose to capitalize on the progress we have made in the structural and dynamic characteriz the type I and type II dimerization and docking (DID) domains of the regulatory subunits of PKA with anchoring partners, the regulatory role of proline isomerization in regulating the PKC lifecycle and the role range crosstalk in regulating the activity of type I PKA specific targets. Our Specific Aims are directed towards: I. Elucidating the Structural Basis for the Isoform-Specific Targeting of Type I andType II PKA II. Understanding How Specific Protein Binding Partners Regulate Molecular Switching Event! Lifecycle of PKC And III. Investigating the Role of Anchored PKA in Regulating the Structure and Activity of its Substrates at the Mitochondria